On the other hand, a number of papers have considered AoI minimization problem under EH setting: [1]} for derivation of average AoI for a single source having finite battery capacity, [2]} for derivation of the minimal age policy for EH two hop network, [3]} for average AoI expression for single source EH server, [4]} for AoI minimization for wirelessly powered user, [5]} for sampling, transmission scheduling and transmit power selection for a single source single sink system over infinite time horizon where delay is dependent on the packet transmission energy. The authors in
[6]} considered two source nodes (power grid node and EH sensor node) sending different data packets to a common destination by using multiple access channel, and derived the delay and AoI of two source nodes respectively.
